Weather resistant flameproof paper



PG Feb. 25, 1947 ATENT OFF-ICE WEATHER RESISTANT OF PAPER.

Edwin Romig Langhlin, Penns Grove, and John Lecroy Ayres, Salem, N. 3., and

Paul Jones Mitchell, Jr., Wilmington, Del., assignors to E. I. du Pont de Nemonrs & Company, Wilmlng-' ton, Del., a corporation oi Delaware No Drawing. Application July 27, 1943, Serial No. 4 96,344

This invention relates to flameproof paper and more specifically to weather resistant fiameproof.

paper made flameproof by the addition of anti mony oxides and chlorine-containing organic compounds. v

For the purpose of this specification and the subjoined claims, a flameproof paper is defined as one which, if tested in a draft-free room by putting in contact with an initiating flame, will not continue to flame of its own accord for more than 5 seconds after removal of said initiating flame, and will not sustain combustion by afterglow beyond the charred area upon removal of said initiating flame. The term paper" is to be taken in a generic sense, to include all articles fashioned from cellulosic pulp, such as lightweight sheets, the heavier-weight paper boards, specifically processed papers such as parchment, and articles molded from paper pulp.

This invention has as an object the production of a fiameproof paper, the flameproof qualities of which are weather resistant in the sense that they are not materially impaired by prolonged exposure to weather.

I is a further object of this invention to achieve flameproof qualities in paper by means which do not appreciably alter the important physical characteristics of tensile and bursting strength, flexibility, thickness, porosity, bulk, or even absorbency.

A still further object of this invention is to provide processes by which such paper may be manufactured in a relatively simple manner on a large scale by the use Of conventional paper mill equipment. Other and further important objects of this invention will appear as the description proceeds.

These objects are accomplished by a novel use of antimony trioxide and chlorine-containing organic compounds in the paper, as more fully set forth hereinbelow.

To accomplish flameproofing by means of metallic oxides is not new. It is old to coat paper and textiles with heavy metal oxides such as oxides of tin, lead, antimony, arsenic, bismuth, titanium and the like, and to decrease their com- 1 Claim. (01. 92-3) tinuous film on the surface of the fabric, and since said chlorine-containing organic compounds generally possess also waterproofing qualities, the fabric is thereby rendered'impervious and waterproof. It is also frequently necessary to include auxiliary compounds which play no part in the actual fiameproofing process but which are employed as binders to facilitate the adherence of the insoluble oxide and thereby prevent its removal thru abrasion; other compounds are often included as plasticizers in an effort to overcome the impairment of flexibility,

As a consequence of these surface applications, which, for effective fiameproofing involve-the use of substantial quantities of opaque and insoluble materials, the physical character of the fabric is altered. This would be particularly true in the case of paper, which as a consequence of the coating or impregnation process would be increased in bulk or thickness, altered in color, flexibility and porosity, and so changed in general character as to become frequently unserviceable for many uses.

Furthermore, whereas the application of chlorinated organic compounds to fabric may be 7 by a mordanting process which involves first impregnating the fabric with a solution of a metallic I salt, and then treating the same with a solution bustibility thereby. It is also old to impregnate,

coat, saturate, or otherwise surface-treat textile fabrics with heavy metal oxides and water-insoluble, chlorine-containing organic compounds having fiameproofing qualities. The latter are generally applied from an organic solvent, which sometimes also acts as a vehicle for the metallic oxide. Under these conditions the chlorine-conof another compound which will cause precipitation of a metallic oxide in the fiber. Such a double-treatment process with aqueous solutions could not universally be applied to paper, for if the latter is not absorbent it will not be uniformly impregnated by the aqueous solutions, and if it is absorbent it will generally be disintegrated by the dual impregnation.

Now, according to our present invention, the primary goal of producing a weather resistant, flameproof paper is achieved by methods which obviate many of the serious disadvantages of surface application processes, particularly those which result in alteration of the physical properties of the flameprooied article. We have found that if the antimony trioxide be mixed with the paper fibers before they are formed into a sheet,

taining organic compound is deposited'in a con then quantities of it as high as 20% by weight of 3 the finished sheet may be incorporated into the paper without seriously affecting its essential physical qualities. The product diflers only inappreciably from paper not containing antimony oxide as regards its general physical properties of 3 flexibility, absorbency,.thickness, porosity, etc., except for a minor decrease in strength and a slight lightening of color. Furthermore, according to our invention, we further incorporate into the paper a chlorine-containing organic compound which co-acts in some way with the antimony trioxlde to produce a ilameproof effect of a degree not otherwise obtainable by'using seriously aflected in either event, inasmuch as 2 by the said joint action of the chlorine-containing agent and antimony trioxide, the quantity of either one may be reduced below the point where it might adversely change thequality and appearance of the resultant paper. Moreover,

wet strength materials, color, and all other in gredients or paper-making auxiliaries customary in the fabrication of paper, paper specialties and the like may be included in the furnish and the paper may be formed onconventional equipment.

The flameprooi eflect on paper achieved by the processes of this invention is particularly resistant to weathering in that prolonged leach- I to a highv degree even after continuous leaching in running water orprolonged outdoor exposure does not materially decrease the flameproof quality. However, this ability to withstand weathering is a characteristic of the flame proof whenapplied as a powder or from aqueous emul- 55 sion as described above, does not generally interfere with the natural absorptive qualities of the cellulose fiber. This discontinuous but uniform distribution of the chlorine-containing organic compound diiiers markedly from the type of continuous film resulting from a solvent application, with its attendant changes in physical properties of the paper.

Paper prepared according to this invention may be subjected to the customary after-treatments to further modify its physica1 properties, as for instance by parchmentizing, printing, embossing, or crping.

Without limiting our invention to any 'particular procedure. the following examples are given to illustrate our preferred mode of operation. Parts mentioned are by weight.

In these examples, basis-weight shall be understood as referring to the weight of a ream consisting of 480 sheets of 24" x 36" each,

70 Alum 4 Example 1.--Application in the beater In this method of application the ingredients for fiameproofing may be mixed with the paper pulp any time prior to sheet formation. The color and antimony trioxlde, for example, are added to the beater with or without size followed :by alum. The chlorine-containing organic compound may be added to the beater or continuo ously to the stock at any convenient place ahead of the paper machine, such as at the head box. If it is desired that the paper shall have exceptional wet strength. either of two methods well known to the paper trade may be used for this is purpose: (a) parchmentizing or (b) the use of a wet strength resin such as the condensation product of melamine and formaldehyde.

In the following example typical of sized, unparchmentized paper, olive drab in color, the

w melamine-formaldehyde resin was added at the head box:

- Pounds Unbleached kraft400 freeness (Green) pulp 1.000 91.5% pure antimony trioxlde 200 Chrome Yellow (C. I. No. 1270) 86.5

Metallized (copper) p-nitrophenyl-azo beta-naphthoi' 95 Dispersed copper phthalocyanine 28.7 80 Soluble Prussian Blue (C. I. No, 1288) 1 (Solid basis) polyvinylidene chloride,

emulsion) 'at fan pump 150 Size 20 Alum .20 Melamine-formaldehyde resin.

When formed into a sheet approximately lb. basis-weight this formula produces a fiameproof sheet which retains its flameproof quality ing in running water for several days.

Not all of the antimony trioxlde and polyvinylidene chloride, however, are retained in the sheet. Part of these agents are lost in the white 3 water until equilibrium is established. Analysis showed'that approximately 9 to 11% of the total weight of the sheet was antimony trioxlde and about 12 to 14% polyvinylidene chlorine.

In the above process, it is not necessary that 80 the chlorine-containing resin be in emulsicn form. The finely powdered product may be added directly to the beater as in the following example using polyvinyl chlorine-diethyl fumarate interpolymer.

Example 2.A'iding chlorinated resin in powdered form This example deals with the production of m unsized, absorptive paper.

'Metallized (copper) p-nitrophenyl-azobetanaphthol 47 Dispersed copper phthalocyanine 29 Powdered (200 mesh) polyvinyl chloridediethyl fumarate interpolymer The sheet is formed in the same manner as above, and possesses weather resistant fla'meproof qualities. It possesses the essential feel, absorptiveness and other physical qualities of ordinary waterleaf, and may be used for preparing parchment paper as in Example 5 hereinbelow.

Example 3.--Beater application of antimony moxide and subsequent impregnation with chlofinated resin In this process paper containing beater-applied antimony trioxide and color is impregnated subsequent to sheet formation with an aqueous mulsion of the chlorine-containing resin. This wrocess is applicable to both sized sheets and waterleaf for parchmentizing. The following is a typical formula for sized. dark-green, highwet-strength paper.

' Pounds Unbleached kraft-400 freeness (Green) pulp 1,000 91.5% pure antimony trioxide n 200 Chrome Yellow (C. I. No. 1270) 112 Metallized (copper) p-nitrophenyl-azobeta-naphthol 30 Dispersed copper phthalocyanine 24 Rosin size 20 Alum 25 Melamine-formaldehyde resin. 15

After forming into a sheet this paper was impregnated at the size press, while still approximately 30% wet, with an aqueous emulsion of polyvinylidene chloride so that it retained, upon drying, 8 to 12% polyvinylidene chloride (dry weight).

In this process if a heavy weight sheet is formed, the chlorinated compound may be applied at the calender stacks, for example, as follows:

Example 4.-Heaoy sheet A sheet of 90 lb. basis-weight, formed from the following typical formula;

V Pounds Unbleached kraft 1,000 91.5% pure antimony trioxide 200 Chrome yellow (C. I. No. 1270) 112 Metallized (copper) p-nitrophenyl-azobeta-naphthol 30 Dispersed copper phthalocyanine 24 Size 25 Alum 25 was surface treated at the calender stacks to pick up 5 to 8% polyvinylidene chloride applied from an aqueous emulsion.

This invention is also adaptable to the production of parchmentized paper. The following is a formula for a water-leaf sheet to be parchmentized:

' Example 5.-Parchment paper Pounds Unbleached kraft-400 freeness 1,000 91.5% pure antimony trioxide 200 Chrome yellow (C. I. No. 1270) 48.5

Metallized (copper) p-nitrophenyl-azobeta-naphthol 14.3 Dispersed copper phthalocyanine 15.5 Alum 40 This formula is formed into a 30 1b. basis-- weight bibulous sheet and treated at the size press with an aqueous emulsion of the interpolymer of vinylidene chloride and up to 15% vinyl chloride so that approximately is retained by the paper. The sheet may now be parchmentized by treatment with sulfuric acid in the usual manner. The resulting paper is characterized by retaining a high degree of flameproofness 6 even after exposure to weather for several months.

Example 6.Twtsting paper A light-weight sheet fiameproofed in this manner may be used for twisting as in the following example:

. Pounds Unbleached kraft-400 freeness 1,000 Antimony trioxide 200 Chrome yellow (C. I. No. 1270) 86.5 Metallized (copper) p-nitrophenyl-azobeta-naphthol Dispersed copper, phthalocyanine 28.75 Prussian blue (0. I. No. 1288) 1 Alum 25 Melamine-formaldehyde 50 A 30 lb. basis-weight bibulous sheet is formed from this formula and treated at the size press with an emulsion of polyvinyl chlorlde-diethyl i'umarate interpolymer (95:5) so that about 20% is retained by the paper. The paper is then twisted.

The coloring of paper is not an essential part of this invention, and an uncolored sheet may be made. for instance, as follows:

Example 7.Uncolored sheet I Pounds Unbleached sulflte pulp 1,000 91.5% pure antimony trioxide 250 Chlorinated paraflln (containing 54% chlorine) as a 30% emulsion 300 Size 20 Alum 30 The sheet is formed as in Example 1.

Example 8.--0.016 natural Fourdrinier kraft board for conversion into corrugated boxes Pounds Unbleached kraft 1,000 Antimony oxide 220 Polyvinyl chloride-dlethyl fumarate interpolymer from 19% aqueous emulsion.. 150 Rosin size 10 Alum 40 The sheet is then formed on a Fourdrinier machine in the usual manner. This sheet may then be converted by customary procedure into corrugated board, and fashioned into boxes which exhibit the property of being flameproof even after exposure to weather.

Example 9.Yellow kraft lined newsboard 0.009

Liner furnish.

Pounds Waste kraft clippings 1,000 Antimony oxide 220 6 oz. metanil yellow (C. I. 138) 1 Rosin size 7 Alum 35 The sheet is formed on a cylinder machine and surface treated at the calender stacks with polyvinylidene chloride 32% emulsion to pick up 7%.

Example 10.Red 45 lb. basis-weight high-wetstrength. absorbent paper Pounds Semi-bleached kraft 1,000 Antimony oxide 200 Fast scarlet 435 (C. I. 327) 12 Powdered polyvinyl chloride 220 Cellulose regenerated from viscose for wet r strength Alum so Pounds Unbleached sulflte 1,000 Antimony oxide 250 Methyl violet (C. I. 680) 1 Victoria green (C. I. 657) 8 Chlorinated polymyrcene from aqueous emulsion 175 Size 20 Alum 35 Example 12.-Article of moulded pulp Pounds Groundwood 1,000 Antimony oxide 200 Powdered polyvinyl acetate-trichlorethylene lnterpolymer 250 Copper phthalocyanine blue 25 Wax-methacrylate resin size 90 Alum 65 The above furnish was dewatered in pulp molding equipment and dried. The molded article possessed flameproof qualities durable to weather.

Example 13.Kraft specialty sheet The sheet, after formation on a Fourdrinier machine, is saturated at the sizepress with an aqueous emulsion of an interpolymer of polyvinylidene chloride and polyvinyl chloride calculated to deposit on the weight of the dry paper. After drying, the sheet is over-printed with a design to simulate foliage and is suitable for use in outside decorations, in view of its weather resistant flameproof qualities.

Although the omission of the organic solvent is one of the major economic advantages in our improved process, such solvents may nevertheless be used in the second stage of the process typifled by Examples 3 and 4 above, 1. e., after incorporation of the metallic oxide through the pulp stage. For instance, one could apply in the second stage a solution of chlorinated polymyrcene in carbon tetrachloride, a solution of chlorinated stearic acid in a 1:1 alcohol-water solution, a solution of a chlorine-containing vinyl-resin in toluene and so on.

As will be seen from the aforegoing examples, the nature of the auxiliary chlorine-containing organic compound employed and its amount may vary within wide The quantity to be employed depends first of all on the amount of HCl liberated by the particular compound when heated to about the kindling temperature of paper, and secondly on the quantity of antimony oxide it is intended to replace. In other words,

it varies somewhat inversely with the quantity of antimony oxide employed per unit weight of paper. It is also dependent to some extent on the thickness of the sheet to be produced, and is best determined experimentally for any particular set of conditions. The process of Example 3 above lends itself particularly to such evaluation, as illustrated by the following example applied to a waterleaf sheet:

8 Example 14 Pounds Unbleached Kraft-400 freeness (Green) pulp I 1.000 Antimony trioxide9l.5% pure 200 Chrome Yellow (0. I. No. 1270) 48.5

Metallized (copper) p-nitrophenyl-azobeta-naphthol 14.3 Dispersed copper phthalocyanine 15.5 Alum 40 laboratory with emulsion or organic solvent solutions of the chlorine-containing organic compound to determine the least amount necessary for fiameproofing. Any resins which were not available in emulsion form were impregnated from a solution in a volatile solvent for purposes of evaluation. After drying, the gain in weight was noted. These strips were then tested for flameproofness by igniting a piece A inch wide in the low blue flame of a Bunsen burner. Increasing quantities of the chlorine-containing agent to be tested were used on successive strips until a point was reached where the flame was immediately extinguished upon removing the strip from the burner. The following is a list of the compounds found feasible for flameproofing paper and the minimum percent (based on the weight of the treated paper) necessary to attain the special degree of flameproofness assumed above for this comparative study:

Per cent weight Minimum of HCl liberated quantity Tom] at designated needed in chlorine temperature above Compound mmem example,

by per cent per 0 u 0 weight 0! am 300 treated C. C. 0. sheet Polyvinylidene chloride. 72 i. 2 45. 7 52. 9 l2 3 Polyvinyl chloride-diethyl fumarate interpolymer 54 4. 0 29. l 44. 1 18.0 Chlorinated polyvinylchloride 65 5. 7 33. 3 53. 3 l7. 0 Polyvinyl chloride 57 2. 7 25. 5 50. 4 2A. 0 Chlorinated polymyroene C! l. 8 30. 8 46. 1 17.0 62% chlorinated .stearic ac 52 2. 3 32. 6 37. 8 31. 0 54% chlorinated paraffin. 54 0. 2 23. 6 43. 5 :55. 0 40% chlorinated paraflln. 40 0. 3 19.0 33. 7 43. 0 Chlorinated myrcene (i7. 5 31. 3 30. 0 65% chlorinated rubbeiz. 65 19. 0

It will be noted that the minimum quantity of chlorine-containing organic compound per unit sheet weight to achieve a specified degree of flameproofness varies inversely with the percentage HCl liberated by this compound at the kindling temperature, and that the product of the two is approximately constant for certain groups of organic compounds. Thus, for polymerized resins, the product of the datum in the fifth column by that in the third column is between 5 and 6 The same product for the unpolymerized compounds is about 8 to 9.5 This product will be designated as the hydrogenchloride equivalent of the given organic compound. If the SbzOa content is at its highest (20%), the requisite hydrogen-chloride equivalent is 2% for polymeric resins and 3% for unpolymerized organic compounds.

To summarize all the above, the chlorinated organic compounds found most suitable in our invention are those which possess at least 40% of heated alone for five minutes at a temperature between 300 and 400 0., which corresponds to the average kindling point of untreated paper.

Organic compounds of lower chlorine content,

say 25 to 30%, may also be used, provided larger tetroxide or any other oxide of antimony may be employed. The quantity thereof may vary from V to by weight based on the weight of the flnal sheet.

The advantages and utility of this invention will now be readily apparent.

This invention may be used. to provide flameproof paper for a large number of uses such as: camouflage, decorations, stage settings, draperies, packaging, insulation for electric equipment, seat covers, upholstery, rugs and many others. It may be used in molded pulp articles such as ash trays.

This invention is advantageous in that the fiameproofing processes by which it may be' achieved need not detract from the physical properties of the resulting paper to an extent inconsistent with good practice. The paper retains most of its strength, may be dyed, printed, parchmentized, or twisted in the same manner as untreated paper.

Furthermore the application of the fiameproofing agents may be easily adapted to most types of paper or mill conditions. Thus (1) the antimony trioxide and chlorine-containing compound, either emulsion or powder, may be added to the paper pulp prior to sheet formation, or (2) the antimony trioxide may be added to the pulp prior to sheet formation and the chlorinecontaining resin, emulsion or solution in solvent, may be applied to the sheet at any convenient point after sheet formation, at the size press or calender stacks for example.

10 Finally this invention is particularly advan tages in that the flameproof properties of this paperare not destroyed by weathering or exposure to water. In fact, in some cases. as for instance in the case of bibulous paper, the flameproof quality may be more durable to weath-' er than the paper itself.

For the purpose of this application and the claims below, a flameproof eiIect on paper shall be considered as weather resistant or as notmaterially impaired by prolonged exposure to weather if a sample of the paper after being submitted to a continuous leaching test in running water at room temperature F.) for 24 hours followed by drying, still exhibits flameproofness to an extent as defined in the intro-, ductory paragraphs of this specification.

We claim:

A flameproof parchment paper containing, uniformly distributed throughout its mass, from 5 to 20% of antimony oxide, based on the weight of the paper, and from 5 to 25% of a chlorinecontaining, water-insoluble, organic compound of the group adapted to liberate hydrogen chloride at the kindling temperature of the paper, the said parchment paper being characterized by a flameproof quality which is weather-resistant.

EDWIN Rome LAUGHLIN. JOHN LECROY AYRES. PAUL JONES MITCHELL, Ja.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS OTHER REFERENCES American Dyestufi Reporter, July 5, 1943, pages 297 to 801.

Number Patent No. 2,416,447.

Gertificate of Correction February 25, 1947. EDWIN ROMIG LAUGHLIN ET AL. 1

It is hereby certified that errors appear in the Cprinted specification of the above numbered patent requiring correction as follows: olumn 7 ginmng with the word Pounds strike out all to and including Alum 35 a m line 14, and insert instead the following- Unbleached sulfite Pounds 1, 000 Antimony oxide do 250 Methyl violet (C. I. 680) do 1 Victoria green (G. I. 657) Ounces 8 Chlorinated polymyrcene from aqueous emulsion Pounds t 175 Size ...d0 20 Alum 4 -do 35 ,column 10, lines 1 and 2, for advantages read advantageous; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent .OflEice.

Signed and sealed this 27th day of May, A. D. 1947.

LESLIE FRAZER,

First Acetate/at Oommiasiwer of Patents.

line 6, Example 11, be- 

